Dynamical inductive charging systems for electric vehicles are an option for future electric mobility concepts and worldwide subject of a high number of research activities and pilot projects. Principally, those systems consist of an electrified road featuring a number of individual sequential “primary” coils for power transmission under the road surface and a secondary “pickup” coil mounted under the floor of the electric vehicle. The coils in the road are connected to a charging infrastructure which activates the coil element under the moving vehicle as soon as both coils are optimally positioned, such creating a nearly static configuration from the vehicle point of view. Optimally in this context means for example, that the position is the position at that one of the coils is penetrated entirely by the electro-magnetic field generated by other of the coils, or at which both coils are in the position where the electromagnetic coupling has a maximum value. Due to road construction or vehicle configuration, the coils may also be activated when they are less than optimally positioned, e.g. whenever they are in a position allowing any electromagnetic coupling.
In order to optimize control of charging, to monitor the performance of the infrastructure or to monitor the performance of the vehicle's charging system, differentiation between primary side and secondary side originated efficiency during power transmission is desirable.
A simple measurement of transmitted and received power however only reveals the mathematical product of vehicle originated efficiency, infrastructure originated efficiency and an efficiency value due to power loss originating from a lateral displacement of the pickup coil and the primary coil. There is no way to differentiate the individual power loss contributions from this measurement.
Therefore, to determine the individual efficiencies, the efficiency of individual vehicles needs to be measured using a calibrated test environment, for example a calibration road. Efficiency of the road infrastructure also needs to be derived from measurements using a calibrated vehicle and a calibrated test track. To characterize the effect of lateral misalignment of primary and secondary coils, predefined passes or trajectories have to be driven with the vehicle on the calibration test track.
This method involves high effort, is costly and does not allow for continuous monitoring of the road infrastructure and the electric vehicles.